1. Risk factors for extensive ulcerative colitis and ulcerative proctitis: a population based case-control study. Issue 12 (December 1991) Authors: Samuelsson, S M; Ekbom, A; Zack, M; Helmick, C G; Adami, H O Journal: Gut Issue: Volume 32:Issue 12(1991) Page Start: 1526 Record Type: Journal Article View Content: Available online (eLD content is only available in our Reading Rooms) ↗